Pain

Question 1

A-beta fibers

Answer 1

non-noxious mechanical stimulus

Question 2

A-delta fibers

Answer 2

noxious mechanical stimulus

Question 3

C fiber

Answer 3

noxious heat and chemical stimuli

Question 4

Are pain signals mainly contralateral or ipsilateral?

Answer 4

contralateral

Question 5

arrange the following from least to most myelinated:
- A-delta fibers
- C fiber
- A-beta fibers

Answer 5

C fiber < A-delta < A-beta

Question 6

nociception

Answer 6

neural encoding of pain

Question 7

pain

Answer 7

unpleasant sensory and EMOTIONAL experience associated with actual/potential damage

Question 8

analgesic

Answer 8

block pain sensation ONLY

Question 9

local anesthetic

Answer 9

block nerve conduction and ALL sensation

Question 10

general anesthetic

Answer 10

cause unconsciousness (not always analgesia)

Question 11

hyperalgesia

Answer 11

enhanced response to painful stimulus

Question 12

allodynia

Answer 12

generation of painful response to an innocuous stimulus

Question 13

Which fiber is associated with first pain and second pain?

Answer 13

first pain = A-d fibers
second pain = C fibers

Question 14

What is acute pain treated with?

Answer 14

local anesthetics

Question 15

what is chronic/persistent pain caused?

Answer 15

release of bradykinin, histamine acid metabolites, and prostaglandins (inflammatory factors)

Question 16

What is chronic pain treated with?

Answer 16

non-steroidal anti-inflammatory drugs
(i.e. NSAIDs like aspirin or ibuprofen)

Question 17

what is deep pain treated with?

Answer 17

major analgesics (opioids) such as morphine

Question 18

What is neuropathic pain defined as?

Answer 18

“pain induced by injury to/disease of the somatosensory system”

(i.e. resulting from nerve injury or infections of the nervous system)

Question 19

examples of neuropathic pain

Answer 19

• phantom limb pain
• trigeminal neuralgia
• shingles
• diabetic neuropathy
• fibromyalgia

Question 20

key point to remember about neuropathic pain?

Answer 20

outlasts healing of original injury

Question 21

clinical features of neuropathic pain

Answer 21

• allodynia
• hyperalgesia
• causalgia
• shooting pains

Question 22

List the endogenous opioids

Answer 22

• met- and leu-enkephalin
• beta-endorphins
• dynorphins
• endomorphins

Question 23

what is the opioid receptor mechanism of action on neurons?

Answer 23

• Gi/o
• 1) inhibit adnenylyl cyclase –> lower cAMP
• 2) increased K+ conductance (hyperpolarization)
• 3) suppression of N-type Ca2+ channel current
• 4) decreased NT release

Question 24

describe the descending path of pain signal modulation (i.e. what is the source of endogenous opioids? where do inhibitory signals go?)

Answer 24

• PAG = source of endogenous opioids
• send inhibitory signals toward RVM and spinal dorsal horn

Question 25

What are the opioid sites of action?

Answer 25

1. PNS --> reduce neurogenic inflammation 2. cingulate cortex --> alter suffering (psychological response to pain) 3. terminals of afferent A-d and C fibers in dorsal horn of SC --> reduce NT release 4. N-type Ca2+ channels --> reduce release of acidic AA and co-transmitter Substance P in substantia gelatinosa

Question 26

What are the pain fibers?

Answer 26

- A-d - C

Question 27

how do opioids modulate/disable descending pain? (hint: inhibition)

Answer 27

opioids inhibit GABA interneurons from inhibiting endogenous pain inhibitory mechanisms

Question 28

What do differences in the properties of different opioids result from?

Answer 28

differences in: - pharmacokinetics - affinity for different opioid receptor subtypes

Question 29

What are the opioid receptor sites?

Answer 29

MOR, DOR, KOR

Question 30

List the major effects of opioids.

Answer 30

1. analgesia 2. sedation and mental clouding 3. euphoria and tranquility 4. antitussive 5. depression of respiratory center (prebotzinger complex) 6. nausea, vomiting

Question 31

which opioid receptors are involved in analgesia?

Answer 31

MOR and KOR

Question 32

Which opioid receptors are involved in euophoria?

Answer 32

MOR and DOR

Question 33

which opioids' side effects can be used to control diarrhea?

Answer 33

- diphenoxylate - loperamide

Question 34

which opioid's side effects can be used to suppress cough?

Answer 34

dextromethorphan